Truing device and truing method for grinding wheel

ABSTRACT

A truing apparatus for a grinding wheel is provided with a truing tool which is held so as to rotate, and the grinding wheel which is rotating is subjected to truing by the truing tool. The truing tool includes a peripheral surface truer having a truer surface formed on its rotating peripheral surface, and an end surface truer having a truer surface formed on its end surface in a direction of a rotation axis thereof. The rotation axis of the truing tool is arranged substantially perpendicularly to a rotation axis of the grinding wheel so that an end surface of the grinding wheel may be corrected with the peripheral surface truer, and a peripheral surface of the grinding wheel may be corrected with the end surface truer.

TECHNICAL FIELD

The present invention relates to a truing apparatus for a grinding wheel for correcting the grinding wheel which is a working tool of a grinding machine, and a truing method.

BACKGROUND ART

In case of conducting thrust grinding or plunge grinding on an end surface of a flange portion or the like of a work, it is necessary to correct (hereinafter also referred to as “truing”) a peripheral surface and end surfaces of a grinding wheel by means of a correcting tool. In a conventional truing apparatus for a grinding wheel, a tool including a diamond truer in a disc-like shape which is provided with a cup-shaped truer on a side surface thereof is used as the correcting tool, and a rotation axis of the correcting tool is arranged in the same direction as a rotation axis of the grinding wheel, whereby the peripheral surface of the grinding wheel is trued with an outer peripheral surface of the diamond truer in a disc-like shape, and the end surfaces of the grinding wheel are trued with an end surface of the cup-shaped truer.

By the way, in case where the end surfaces of the grinding wheel are trued with the end surface of the cup-shaped truer, a contact area between the grinding wheel and the correcting tool is increased, and there is a problem that tip ends of grains of the grinding wheel may come into contact with the correcting tool more than required, and the tip ends of the grains are likely to be flattened, resulting in deterioration of cutting quality of the grinding wheel. Under the circumstances, as disclosed in Patent Document 1, it is proposed that the rotation axis of the diamond truer in a disc-like shape is arranged perpendicularly to the rotation axis of the grinding wheel so that the end surfaces of the grinding wheel may be trued with the outer peripheral surface of the diamond truer in a disc-like shape.

The applicant had already known the following document, at a time of filing this application, as the document in which the above described technical information is disclosed.

Patent Document 1: Japanese Patent Publication No. JP-A-2002-283235

However, in the truing method disclosed in Patent Document 1, in order to true both the peripheral surface and the end surfaces of the grinding wheel, it is necessary to provide a truing apparatus for truing the peripheral surface of the grinding wheel, in addition to a truing apparatus for the end surfaces, and hence, cost related to the truing apparatus will be increased. At the same time, in case of mounting the truing apparatuses on a grinding machine or the like, a space for installing these truing apparatuses will be required, and there is a problem that the grinding machine is upsized.

On the other hand, in case where the end surfaces of the grinding wheel are trued with the cup-shaped truer, contact pressure is decreased, because contact between the grinding wheel and the correcting tool is surface contact. As the results, the grains are not sufficiently crushed to form a sharp cutting edge. Moreover, the same grain is rubbed with the truer many times, because continuous contacts are made along a rotation direction of the cup-shaped truer, and edge tips of the grains are worn and flattened. Therefore, there is a problem that cutting quality of the grinding wheel cannot be enhanced, and grinding burning is likely to occur, when a work is ground by this grinding wheel.

In view of the above, it is conducted to decrease the grains to be contacted with the correcting tool, by using the grinding wheel having low density of the grains, thereby to relatively increase contact pressure against the grains. In this manner, the grains are sufficiently crushed to form a sharp cutting edge, and contacts with the grains are reduced, whereby occurrence of grinding heat is restrained. However, in this case, there is a problem that grinding efficiency is deteriorated and useful life of the grinding wheel is shortened, because of the low density of the grains of the grinding wheel and the small number of the grains to be contacted with the work.

DISCLOSURE OF THE INVENTION

The invention is made in view of the above described circumstances, and it is an object of the invention to provide a truing apparatus for a grinding wheel and a truing method in which cutting quality of a peripheral surface and an end surface of the grinding wheel is enhanced, and occurrence of grinding burning at a time of grinding a work can be restrained.

In order to solve the above described problem, a truing apparatus for a grinding wheel according. to the invention, is “characterized by comprising

a correcting tool which is held so as to rotate for correcting the grinding wheel which is rotating,

the correcting tool including a peripheral surface truer having a truer surface formed on its rotating peripheral surface, and an end surface truer having a truer surface formed on its end surface in a direction of a rotation axis thereof,

wherein the rotation axis of the correcting tool is arranged substantially perpendicularly to a rotation axis of the grinding wheel so that an end surface of the grinding wheel may be corrected with the peripheral surface truer, and a peripheral surface of the grinding wheel may be corrected with the end surface truer”.

Herein, as “the peripheral surface truer”, “a truer in a disc-like shape” can be exemplified, and as “the end surface truer”, “a cup-shaped truer” and “a truer having one or a plurality of ribs” can be exemplified. Moreover, the peripheral surface truer and the end surface truer may be those employing diamond grains or the like, or may be those employing columnar diamonds.

It is to be noted that the term “truing” is used as including both truing in a strict sense and dressing. In other words, both a work for adjusting a shape of the grinding wheel and a work for adjusting surface condition of the grinding wheel are named as truing. Truing is, for example, to adjust an outer peripheral surface of the grinding wheel to a desired shape, whereas dressing is to adjust surface condition of a grinding surface of the grinding wheel, that is, to correct a drop, crush, clogging and so on. However, truing and dressing are not strictly discriminated as practical terms for field use. Both an apparatus for truing and an apparatus for dressing are called as a truing apparatus or a dressing apparatus in the same manner. It is considered that this is because when truing the grinding wheel is conducted, dressing is also completed at the same time, in many cases.

According to the invention, after the rotation axis of the correcting tool is arranged substantially perpendicularly to the rotation axis of the grinding wheel, the end surface of the grinding wheel is trued with the peripheral surface truer, and the peripheral surface of the grinding wheel is trued with the end surface truer. In this manner, on both the end surface and the peripheral surface of the grinding wheel, contact between the grinding wheel and the correcting tool is made in a form of point contact or linear contact, whereby the contact area between them can be made as small as possible. As the results, it is possible to prevent the correcting tool from rubbing grains of the grinding wheel more than required to wear edge tips of the grains to be flattened, and at the same time, it is possible to increase contact pressure against the grinding wheel. Accordingly, the grains of the grinding wheel can be crushed in a favorable state to obtain a sharp cutting edge, and cutting quality of the grinding wheel can be enhanced.

Therefore, occurrence of grinding burning when a work or the like is ground can be restrained, and occurrence of grinding heat can be also restrained. As the results, influence of heat on the work is reduced, and working accuracy can be enhanced. Particularly, when grinding work such as thrust grinding or plunge grinding on an end surface of a flange portion or so of the work is conducted, occurrence of grinding burning can be restrained.

Moreover, because the edge tips of the grains of the grinding wheel can be made sharper, durability of the edge tips of the grains by the grinding work can be enhanced. As the results, intervals of conducting truing (truing intervals) are prolonged, and hence, working efficiency of the grinding machine is enhanced, whereby productivity can be improved.

Further, because the contact pressure against the grinding wheel can be increased, the correcting tool can be contacted with more grains than in the conventional truing apparatus, when the truing is conducted, and it is possible to correct the grinding wheel having higher grain density than before. In other words, because the grinding wheel having the higher grain density can be favorably corrected, it is possible to mount the grinding wheel having the high grain density on the grinding machine to conduct the grinding work, and hence, grinding efficiency of the grinding machine can be enhanced.

Further, because the correcting tool having the peripheral end truer and the end surface truer is used, both the end surface and the peripheral surface of the grinding wheel can be trued with the single truing apparatus. Therefore, increase of the cost related to the truing apparatus can be restrained, and upsizing of the grinding machine can be restrained. Moreover, because the rotation axis of the correcting tool is arranged substantially perpendicularly to the rotation axis of the grinding wheel, a disk-shaped surface of the correcting tool extends in the same. direction as a direction in which the worktable extends when the truing apparatus is provided on the worktable side of a head stock etc. of the grinding machine. Therefore, a protruding amount of the truing apparatus from the headstock etc. can be reduced, and hence, upsizing of the grinding machine can be restrained.

In addition to the above described structure, the truing apparatus for the grinding wheel according to the invention is “characterized in that an inner diameter of the end surface truer of the correcting tool is larger than a grinding width of the grinding wheel”. Herein, “the inner diameter of the end surface truer” means an inner diameter of an annular orbit of the end surface truer which is formed by rotating the correcting tool.

By the way, in case where the peripheral surface of the. grinding wheel is trued with the end surface truer of the correcting tool, after the rotation axis of the correcting tool is arranged substantially perpendicularly to the rotation axis of the grinding wheel, as described above, relative movement of a contact part of the end surface truer to be contacted with the grinding wheel is made in opposite directions at right and left sides of the rotation axis of the correcting tool. As the results, when the end surface truer comes into contact with the contact part at the opposite side beyond the rotation axis of the correcting tool, on occasion of truing the peripheral surface of the grinding wheel with the end surface truer, truing condition with respect to the grinding wheel remarkably changes. Therefore, there is a problem that it becomes difficult to true the grinding wheel in optimum state.

According to the invention, the inner diameter of the end surface truer of the correcting tool is made larger than the grinding width of the grinding wheel to be corrected. As the results, when the peripheral surface of the grinding wheel is trued from one side to the other side along the axial direction of the grinding wheel using the end surface truer, it is possible to prevent the contact part of the end surface truer at the opposite side beyond the rotation axis thereof from getting into contact with the peripheral surface of the grinding wheel. Accordingly, it is possible to prevent a remarkable change of the truing condition while the grinding wheel is trued, and to true the grinding wheel in the optimum state, whereby the same operational effect as described above can be achieved reliably.

Provided that the inner diameter of the end surface truer is B, and the grinding width of the grinding wheel is TW, it is desirable that relation between the inner diameter B and the grinding width TW is within a range satisfying TW<B <1.2TW to 3TW. This is because in case where the inner diameter B of the end surface truer is made larger than this range, the truing apparatus will be upsized and become disadvantageous in respect of space and cost.

In addition to the above described structure, the truing apparatus for the grinding wheel according to the invention is “characterized in that the end surface truer of the correcting tool includes a columnar diamond”.

Herein, as “the columnar diamond”, a polycrystalline diamond formed of a diamond film to be columnar which is synthesized using a known synthesizing process such as CVD process, plasma jet process, flame-fusion process, etc. is preferably employed.

By the way, a monocrystalline diamond is heretofore employed in many correcting tools. However, since the monocrystalline diamond is likely to crack sharply, there is a problem that a surface shape of the correcting tool remarkably changes depending on a manner of cracking, and truing performance of the correcting tool becomes unstable.

According to the invention, the end surface truer including the polycrystalline columnar diamond which cracks minutely is used, whereby the end surface truer is worn substantially uniformly. Therefore, change in the surface shape of the truer can be decreased to the least, and the truing performance can be stabilized.

Moreover, a single or a plurality of the columnar diamonds may be employed in the end surface truer. The end surface truer may be provided with the columnar diamond only, or may be also provided with a holding member for holding the columnar diamond. Further, the peripheral surface truer may be also provided with the columnar diamond.

A truing method of a grinding wheel according to the invention is “characterized in that a rotation axis of a correcting tool which includes a peripheral surface truer having a truer surface formed on its rotating peripheral surface and an end surface truer having a truer surface formed on its end surface in a direction of the rotation axis thereof is arranged substantially perpendicularly to a rotation axis of the grinding wheel, and that an end surface of the grinding wheel is corrected with the peripheral surface truer of the correcting tool, and a peripheral surface of the grinding wheel is corrected with the end surface truer”.

According to the present invention, substantially the same operational effects as in the above described truing apparatus for the grinding wheel can be achieved. Because the grains of the grinding wheel can be crushed in a favorable state to obtain a sharp cutting edge, cutting quality of the peripheral surface and the end surface of the grinding wheel is enhanced, and occurrence of grinding burning on occasion of grinding a work can be restrained.

In addition to the above described structure, the truing method of the grinding wheel according to the invention is “characterized in that in case where the grinding wheel is provided with chamfered parts between the end surface and the peripheral surface thereof, when a predetermined direction with respect to the direction of the rotation axis of the grinding wheel is one side and a side opposite to the one side is the other side, the chamfered part at one side of the grinding wheel is corrected with the other side of the end surface truer, whereas the chamfered part at the other side of the grinding wheel is corrected with the one side of the end surface truer, wherein a rotation direction of the correcting tool is reversed between at a time when the chamfered part at the one side is corrected and at a time when the chamfered part at the other side is corrected”. Herein, as “the chamfered part”, “an R part having an arc shape in section”, “a C part having a rectilinear shape in section”, “a part having other shapes than the R part and the C part in section”, and so on can be exemplified.

According to the present invention, in case of forming the chamfered parts such as the R parts at both ends of the grinding wheel, or in case of correcting the chamfered parts, the grinding wheel and the end surface truer of the correcting tool relatively move in the same direction at the both ends of the grinding wheel so that the truing condition may not change. As the results, in addition to the above described operational effects, it is possible to true the chamfered parts of the grinding wheel in a favorable state.

As described herein above, according to the invention, it is possible to provide the truing apparatus for the grinding wheel and the truing method in which cutting quality of the peripheral surface and the end surface of the grinding wheel is enhanced, and occurrence of grinding burning on occasion of grinding a work can be restrained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically showing a structure of a grinding machine to which an embodiment of a truing apparatus for a grinding wheel according to the invention is applied.

FIG. 2 is an enlarged view showing a correcting tool in the truing apparatus for the grinding wheel as shown in FIG. 1.

FIG. 3A is an explanatory view showing operation mode of the truing apparatus for the grinding wheel in FIG. 1, together with a truing method.

FIG. 3B is an explanatory view showing the operation mode of the truing apparatus for the grinding wheel in FIG. 1, together with the truing method.

FIG. 4A is a plan view showing a correcting tool in another embodiment which is different from the correcting tool as shown in FIG. 2.

FIG. 4B is a plan view showing a correcting tool in still another embodiment which is different from the correcting tool as shown in FIG. 2.

FIG. 5A is an explanatory view showing relation between an inner diameter of an end surface truer in a correcting tool and a grinding width of a grinding wheel in still another embodiment.

FIG. 5B is an explanatory view showing relation between an inner diameter of an end surface truer in a correcting tool and a grinding width of a grinding wheel in still another embodiment.

FIG. 6A is an explanatory view showing a truing method of a grinding wheel provided with an R part.

FIG. 6B is an explanatory view showing the truing method of the grinding wheel provided with the R part.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, an embodiment of a truing apparatus for a grinding wheel and a truing method according to the invention will be described referring to FIGS. 1 to 3B. FIG. 1 is a plan view schematically showing a structure of a grinding machine to which an embodiment of a truing apparatus for a grinding wheel according to the invention is applied. FIG. 2 is an enlarged view showing a correcting tool in the truing apparatus for the grinding wheel as shown in FIG. 1. FIG. 3A and FIG. 3B are explanatory views showing operation mode of the truing apparatus for the grinding wheel in FIG. 1, together with a truing method.

As shown in FIG. 1, a grinding machine 1 to which the truing apparatus for the grinding wheel in one embodiment of the invention is applied includes a bed 2 which constitutes a base part, a grinding wheel head 3 which is mounted on the bed 2 and supports a grinding wheel T so as to be driven to rotate, an X-axis driving unit 4 for moving the grinding wheel head 3 in a direction of X-axis, a worktable 5 which is mounted on the bed 2 at a different position from the grinding wheel head 3, a headstock 7 and a tailstock 8 which are mounted on the worktable 5 to support a work W and have a main shaft 6 for driving the work W to rotate, a Z-axis driving unit 9 for moving the worktable 5 in a direction of Z-axis, and a truing apparatus 11 which is provided on the headstock 7 and has a correcting tool 10 for correcting the grinding wheel T. It is to be noted that the X-axis driving unit 4 and the Z-axis driving unit 9 are known driving units respectively including servomotors, forwarding screws, and so on.

The grinding wheel head 3 is provided with a grinding wheel spindle 12 to which the grinding wheel T is mounted and a spindle head 13 which rotatably supports the grinding wheel spindle 12, and a rotary driving unit 14 including a motor and so on for driving the grinding wheel spindle 12 to rotate. The grinding wheel T is formed in a disc-like shape, employing appropriate grindstone material such as CBN grindstone, so that an outer peripheral surface thereof and end surfaces near the outer peripheral surface may become a grinding surface. The grinding wheel T is driven to rotate together with the grinding wheel spindle 12 by the rotary driving unit 14.

The correcting tool 10 includes a peripheral surface truer 15 in a disc-like shape having an outer peripheral surface formed as a truer surface, and an end surface truer 16 having an end surface projecting in a direction of a rotation axis of the correcting tool 10 formed as a truer surface. In this embodiment, the peripheral surface truer 15 is a diamond truer in a disc-like shape having a diamond metal bonding layer which is publicly known. The end surface truer 16 includes a holding member 17 which is formed in a shape of a rectilinear rib, and a columnar diamond 18 which is embedded in a holding hole formed in the holding member 17 in such a manner that the columnar diamond 18 is exposed from an end surface of the holding member 17 (See FIG. 2).

This columnar diamond 18 is a polycrystalline diamond, which is formed in a columnar shape from a diamond film which is synthesized by a known synthesizing process such as CVD process. The holding member 17 is formed of appropriate material such as metal, for example. In this embodiment, the two columnar diamonds 18 are embedded and held in the holding member 17.

The truing apparatus 11 having this correcting tool 10 further includes a tool table 19 which supports the correcting tool 10 so as to rotate, in such a manner that a rotation axis of the correcting tool 10 may be substantially perpendicular to a rotation axis of the grinding wheel T which is mounted on the grinding wheel head 3. The truing apparatus 11 is further provided with a rotary driving unit (not shown) which includes a motor and so on, for rotatably driving the correcting tool 10 which is rotatably held on the tool table 19.

The grinding machine 1 is further provided with a CNC control device 20 for controlling the X-axis driving unit 4, the rotary driving unit for the main shaft 6, the Z-axis driving unit 9, the rotary driving unit 14 for the grinding wheel T, the rotary driving unit for the truing apparatus 11, and so on. This CNC control device 20 is constructed employing a computer which has a CPU, ROM, RAM, hard disk, etc., and capable of grinding the work W and correcting the grinding wheel T through numerical control, by carrying out predetermined programs.

Then, the truing method of the grinding wheel T in the grinding machine 1 in this embodiment will be described, together with the operation mode of the truing apparatus 11. In case of truing the end surfaces of the grinding wheel T, the CNC control device 20 controls the X-axis driving unit 4 and the Z-axis driving unit 9 to appropriately move the grinding wheel head 3 and the worktable 5 thereby to bring the outer peripheral surface of the peripheral surface truer 15 of the correcting tool 10 into contact with the end surface of the grinding wheel T. Then, in a state where the peripheral surface truer 15 is cut into the end surface of the grinding wheel T by a predetermined amount, the grinding wheel T and the correcting tool 10 are relatively moved in the direction of the X-axis, whereby the end surface of the grinding wheel T is trued with the peripheral surface truer 15 (See FIG. 3A) . This operation is repeated by a predetermined number of times.

In truing the end surfaces of the grinding wheel T in this manner, contact parts between the end surface of the grinding wheel T and the disc-shaped peripheral surface truer 15 become substantially point contact. Therefore, it is possible to prevent the peripheral surface truer 15 from rubbing the grains of the grinding wheel T to wear edge tips of the grains to be flattened, and the grains having a sharp cutting edge can be obtained.

Moreover, in truing the end surfaces of the grinding wheel T, either of the grinding wheel T and the correcting tool 10 is rotated in a reverse direction between at a time when the end surface at one side is trued and at a time when the end surface at the other side is trued, so that the contact parts between the grinding wheel T and the correcting tool 10 may move in the same direction.

On the other hand, in case of truing the peripheral surface of the grinding wheel T, the CNC control device 20 controls the X-axis driving unit 4 and the Z-axis driving unit 9 to appropriately move the grinding wheel head 3 and the worktable 5 thereby to bring the end surface of the end surface truer 16 of the correcting tool 10 into contact with the outer peripheral surface of the grinding wheel T. Then, in a state where the end surface truer 16 is cut into the peripheral surface of the grinding wheel T by a predetermined amount, the grinding wheel T and the correcting tool 10 are relatively moved in the direction of the Z-axis, whereby the peripheral surface of the grinding wheel T is trued with the end surface truer 16 (See FIG. 3B). This operation is repeated by a predetermined number of times.

In truing the peripheral surface of the grinding wheel T in this manner, substantially linear contact is obtained in contact parts between the peripheral surface of the grinding wheel T and the end surface truer 16. However, because this is the linear contact extending in a direction substantially perpendicular to the rotation direction of the end surface truer 16, it is possible to prevent the end surface truer 16 from rubbing the grains of the grinding wheel T more than required to wear edge tips of the grains to be flattened. At the same time, because the contact pressure becomes larger than in case of the point contact, the grains of the grinding wheel T are crushed in a favorable state, whereby a sharp cutting edge can be obtained.

Moreover, in this embodiment, a cutting amount is 2 to 3 micron, and the number of repetition is 5 to 10 times, when the end surface of the grinding wheel T is trued with the peripheral surface truer 15, whereas a cutting amount is about 5 micron in diameter, and the number of repetition is four to five times, when the peripheral surface of the grinding wheel T is trued with the end surface truer 16. Further, as compared with the grinding wheel which is trued by the conventional truing apparatus for truing the end surfaces of the grinding wheel with the cup-shaped truer, the grinding wheel T which is trued by the truing apparatus 11 in this embodiment improves by about ten times in grinding efficiency and by about 20 times in truing interval.

In this manner, according to the truing apparatus 11 for the grinding wheel and the truing method in this embodiment, the rotation axis of the correcting tool 10 is arranged substantially perpendicularly to the rotation axis of the grinding wheel T, and thereafter, the end surfaces of the grinding wheel T are trued with the peripheral surface truer 15, and the peripheral surface of the grinding wheel T is trued with the end surface truer 16. Consequently, on both the end surfaces and the peripheral surface of the grinding wheel T, the contact between the grinding wheel T and the correcting tool 10 becomes the point contact or linear contact, whereby the contact area between them can be decreased to the least. Therefore, it is possible to prevent the correcting tool 10 from rubbing the grains of the grinding wheel T more than required to wear the edge tips of the grains to be flattened, and at the same time, it is possible to increase the contact pressure. As the results, it is possible to crush the grains of the grinding wheel T in a favorable state to obtain a sharp cutting edge, and to improve cutting quality of the grinding wheel T.

Accordingly, on occasion of grinding the work W or the like, occurrence of grinding burning and occurrence of grinding heat can be restrained, and hence, influence of heat on the work W is reduced, whereby the working accuracy can be improved. Particularly, when grinding work such as thrust grinding, plunge grinding etc. is conducted on the end surface of a flange portion or so of the work W, occurrence of grinding burning can be restrained.

Moreover, because the edge tips of the grains of the grinding wheel T can be made sharper, durability of the edge tips of the grains by the grinding work can be enhanced. As the results, intervals of conducting truing (the truing intervals) are prolonged, and hence, working efficiency of the grinding machine 1 is enhanced, whereby productivity can be improved. Further, because the contact pressure between the grinding wheel T and the correcting tool 10 can be increased, it is possible to bring the correcting tool 10 into contact with more grains than in the conventional truing apparatus when the truing is conducted, and it is possible to correct the grinding wheel T having higher grain density than before. In other words, because the grinding wheel T having the higher grain density can be favorably corrected, it is possible to mount the grinding wheel T having the high grain density on the grinding machine 1 to conduct the grinding work, and hence, grinding efficiency of the grinding machine 1 can be enhanced.

Further, because the correcting tool 10 having the peripheral surface truer 15 and the end surface truer 16 is used, both the end surfaces and the peripheral surface of the grinding wheel T can be trued with the single truing apparatus 11. Therefore, increase of the cost related to the truing apparatus 11 can be restrained, and at the same time, upsizing of the grinding machine 1 can be restrained. Moreover, because the rotation axis of the correcting tool 10 is arranged substantially perpendicularly to the rotation axis of the grinding wheel T, a disc-shaped surface of the peripheral surface truer 15 of the correcting tool 10 extends in the same direction as a direction in which the worktable 5 extends. Therefore, a protruding amount of the truing apparatus 11 from the headstock 7 can be reduced, and hence, upsizing of the grinding machine 1 can be restrained.

Moreover, because the end surface truer 16 is formed by employing a polycrystalline columnar diamond 18 which is cracked minutely, the end surface truer 16 is worn substantially uniformly, and change of its surface shape can be decreased to the least. Therefore, truing performance can be stabilized.

Still further, in this embodiment, the end surface truer 16 in the correcting tool 10 includes the holding member 17 in a shape of a linear rib in which the columnar diamonds 18 are embedded. However, the end surface truer 16 is not limited to this structure, but may be of such structure that the columnar diamonds 18 are embedded in the holding members of various shapes. Specifically, as shown in FIG. 4A, the end surface truer 16 may be so constructed that a plurality of holding members 25 in a shape of a rectilinear rib respectively having the columnar diamonds 18 embedded therein are provided in a circumferential direction at positions apart from the rotation center of the correcting tool 10 so as to extend in normal directions. Alternatively, as shown in FIG. 4B, the end surface truer 16 may be so constructed that a plurality of the columnar diamonds 18 are embedded in a cup-shaped holding member 26. In both cases, substantially the same operational effects can be obtained.

Then, referring to FIGS. 5A to 6B, a correcting tool 30 which is different from the above described embodiment and a truing method of the grinding wheel T using the correcting tool 30 will be described in detail. FIGS. 5A and 5B are explanatory views showing relation between an inner diameter of the end surface truer and a grinding width of the grinding wheel in the correcting tool in the different embodiment. FIGS. 6A and 6B are explanatory views showing a truing method of a grinding wheel provided with an R part.

As shown in FIGS. 5A to 6B, the correcting tool 30 in this embodiment has substantially the same shape as the correcting tool 10 which is shown in FIG. 4B, and includes a peripheral surface truer 31 in a shape of a disc and an end surface truer 32 in a shape of a cylindrical cup. In the correcting tool 30 in this embodiment, the peripheral surface truer 31 and the end surface truer 32 are diamond truer. It is to be noted that only the end surface truer 32 is shown in section for convenience's same, in FIGS. 5A to 6B.

As shown in the drawings, the inner diameter B of the end surface truer 32 in this correcting tool 30 is larger than the grinding width TW of the grinding wheel T. It is desirable that the inner diameter B of the end surface truer 32 is within a range satisfying TW<B<1.2TW to 3TW. Moreover, the correcting tool 30 may be so constructed that the end surface truer 32 holds the columnar diamond 18, in the same manner as the embodiment as shown in FIG. 4B.

Then, the truing method of the grinding wheel T using the correcting tool 30 will be described. This correcting tool 30 is used in place of the correcting tool 10 which is mounted on the truing apparatus 11 in the grinding machine 1 as shown in FIG. 1, for example. Explanation of end surface truing of the grinding wheel T will be omitted herein, because it is conducted in the same manner as the truing with the above described correcting tool 10.

In case of truing the peripheral surface of the grinding wheel T by this correcting tool 30, when the correcting tool 30 is rotated, regions of the end surface truer 32 at both sides of the rotation axis of the correcting tool 30 become contact parts which can be contacted with the peripheral surface of the grinding wheel T. These contact parts of the end surface truer 32 move in relatively opposite directions at both sides of the rotation axis, and so, the peripheral surface of the grinding wheel T will be trued with the contact part of the end surface truer 32 which moves in the same direction as the direction in which the contact part of the grinding wheel T moves along with the rotation of the grinding wheel T.

Specifically, in case where the grinding wheel T is rotated so that the contact part of the grinding wheel T may move upward in the drawing, and at the same time, the correcting tool 30 provided with the end surface truer 32 is rotated in a counterclockwise direction in the drawing, for example, as shown in FIG. 5A, the contact part of the end surface truer 32 at the right side in the drawing moves in the same direction as the moving direction of the grinding wheel T. Then, the grinding wheel head 3 and the worktable 5 are appropriately moved so that the contact part of the end surface truer 32 at the left side may not come into contact with the peripheral surface of the grinding wheel T, whereby the peripheral surface of the grinding wheel T is trued with the contact surface of the end surface truer 32 at the right side.

Moreover, the inner diameter B of the end surface truer 32 is larger than the grinding width TW of the grinding wheel T, as shown in FIG. 5B, and therefore, even though the grinding wheel T moves inward of the end surface truer 32 along with the peripheral surface truing of the grinding wheel T, the peripheral surface of the grinding wheel T will not come into contact with the contact part of the end surface truer 32 at the left side. Further, relative movements of the grinding wheel T and the end surface truer 32 are controlled by the CNC control device 20 so that the contact part of the end surface truer 32 at the left side, that is, at the opposite side may not come into contact with the peripheral surface of the grinding wheel T.

Then, in case of forming R parts 33 as chamfered parts between the end surfaces and the peripheral faces of the grinding wheel T, as shown in FIGS. 6A and 6B, the R part 33 of the grinding wheel T at the left side in the drawing is trued by bringing the contact part of the end surface truer 32 at the right side into contact with the R part 33 (See FIG. 6A). On the other hand, with respect to the R part 33 of the grinding wheel T at the right side in the drawing, the rotation direction of the end surface truer 32 (the correcting tool 30) is reversed so that the contact part of the. end surface truer 32 at the left side may move in the same direction as the contact part of the grinding wheel T, and thereafter, the R part 33 at the right side is trued, by bringing the contact part of the end surface truer 32 at the left side into contact with the R part 33 (See FIG. 6B).

In the above described truing of the R part 33 of the grinding wheel T too, the X-axis driving unit 4 and the Z-axis driving unit 9 are controlled by the CNC control device 20 to appropriately move the grinding wheel head 3 and the worktable 5, whereby a desired shape of the R part can be obtained.

As described above, according to the truing apparatus 11 for the grinding wheel and the truing method in this embodiment, the inner diameter B of the end surface truer 32 is made larger than the grinding width TW of the grinding wheel T, and at the same time, in case of truing with the end surface truer 32, the truing is conducted in such a manner that the contact part of the end surface truer 32 at the opposite side may not come into contact with the grinding wheel T. Therefore, it is possible to prevent a remarkable change of the truing condition while the grinding wheel T is trued, and it is possible to true the grinding wheel T in the optimum state.

Moreover, in case of truing the R parts 33 at both ends of the grinding wheel T, the contact parts of the grinding wheel T and the end surface truer 32 relatively move in the same direction at both the right and left sides so that the truing conditions may not be different between the R parts 33 at the right and left sides. As the results, the R parts 33 of the grinding wheel T can be trued in a favorable state.

Although the invention is described herein by way of an embodiment in the best mode for carrying out the invention, the invention is not limited to this embodiment, but various improvements and modifications of design can be made within a scope not deviating from the gist of the invention, as described below.

Specifically, although in this embodiment, the end surface truer 16 in the correcting tool 10 is provided with the columnar diamonds 18, the end surface truer 16 is not limited to this, but the end surface truer 16 may be provided with the diamond grains in the same manner as the peripheral surface truer 15. Alternatively, the columnar diamonds may be embedded in the peripheral surface truer 15. The substantially same operational effects as above can be obtained with such structures.

Moreover, although in this embodiment, the invention is applied to the grinding machine 1 for grinding a cylinder, the invention is not limited to the case. For example, the invention can be applied to grinding machines of various types, such as a C-X axes synchronous pin grinding machine for grinding a crank shaft or the like, a screw grinding machine, an inner surface grinding machine, and so on. It is desirable that the invention is applied to a grinding machine for grinding such a work that grinding work must be conducted on an end surface of a flange portion or the like. 

1. A truing apparatus for a grinding wheel, comprising: a truing tool which is held so as to rotate and executes truing on the grinding wheel which is rotating, the truing tool including a peripheral surface truer having a truer surface formed on a rotating peripheral surface thereof, and an end surface truer having a truer surface formed on an end surface thereof in a direction of a rotation axis thereof, wherein the rotation axis of the truing tool is arranged substantially perpendicularly to a rotation axis of the grinding wheel so that an end surface of the grinding wheel is subjected to truing with the peripheral surface truer, and a peripheral surface of the grinding wheel is subjected to truing with the end surface truer.
 2. The truing apparatus wheel according to claim 1, wherein an inner diameter of the end surface truer of the truing tool is larger than a grinding width of the grinding wheel.
 3. The truing apparatus according to claim 1, wherein the end surface truer of the truing tool includes a columnar diamond.
 4. A truing method of truing a grinding wheel including an end surface and a peripheral surface, the method comprising: providing a truing tool, which includes a peripheral surface truer having a truer surface formed on a rotating peripheral surface thereof, and an end surface truer having a truer surface formed on an end surface in a direction of the rotation axis thereof; arranging the truing tool so that a rotation axis of the truing tool are substantially perpendicular to a rotation axis of the grinding wheel; executing truing on the end surface of the grinding wheel with the peripheral surface truer of the truing tool; and executing truing on a peripheral surface of the grinding wheel with the end surface truer.
 5. The truing method according to claim 4, wherein the grinding wheel is provided with a first chamfered part between one of the opposite end surfaces and the peripheral surface at one side in the direction of the rotation axis of the grinding wheel, and a second chamfered part between the other opposite end surface and the peripheral surface at the other side in the direction of the rotation axis of the grinding wheel, the first chamfered part is subjected to truing with a part of the end surface truer at the other side while the truing tool is rotated in a first direction, and the second chamfered part is subjected to truing with a part of the end surface truer at the one side while the truing tool is rotated in a second direction opposite to the first direction.
 6. The truing apparatus according to claim 2, wherein the end surface truer of the truing tool includes a columnar diamond. 